This invention relates to soluble coffee and more particularly to the preparation of a soluble coffee of improved stability during storage.
The use of conventional spray drying techniques to prepare soluble coffee from an aqueous extract has long been known to result in a loss of desirable volatile constituents responsible for the characteristic aroma and flavor of fresh coffee. The addition of aroma concentrates such as coffee oil or distilled aroma fractions to the coffee powder after spray drying has been used in an effort to replace these lost aromatics but use of such methods has generally not resulted in obtaining a final product equal in quality to the undried extracts. Also, difficulties have been encountered in the preparation of good quality aroma concentrate.
Processing variations such as low-temperature spray drying and freeze drying have generally proven successful in varying degrees in preventing the volatilization of the desirable aromatics. However, it has been found that increased retention of these aromatics is more likely to lead to the development of off-flavors in the coffee after several months of storage. The development of these off-flavors is believed to be cause by caused reaction of two or more of the aromatic constituents in the coffee rather than by the presence or decomposition of a single component. Selective removal of one or all of the reactive constituents, then, while inhibiting the reaction to off-flavors during storage, results in the loss of the removed constituent's desirable aroma and flavor contribution and also the removal of other flavor notes. Chemical conversion of the off-flavor precursors to non-reactive products, such as described in U.S. Pat. No. 3,482,988, similarly results in the loss of the independent, desirable aroma and flavor contribution imparted to the coffee by the reactive constituents.
It is accordingly an object of this invention to prepare a soluble coffee containing nearly all the original aromatic constituents present in the coffee extract but which does not develop off-flavors during storage.